1. Field of the Invention
This invention relates to a method of stabilizing diesel fuels by improving the storage stability and, also, preventing oxidation of such fuels.
2. Description of the Background Art
One of the problems associated with diesel fuels is excessive sediment formation, which is ascribed to oxidation under field storage conditions. The presence of sediment can interfere with the normal operation of diesel engines and can cause severe damage to engine parts. Diesel fuels which are susceptible to oxidation are typically characterized as unstable.
U.S. Pat. No. 4,698,169 describes a product made by reacting an alkenylsuccinic compound with an arylamine and an alkanolamine, an aminomethane or a hindered alcohol. The product is reported as providing dispersant and antioxidant activity to lubricant compositions when incorporated therein.
U.S. Pat. No. 4,089,794 describes substantially saturated polymers comprising ethylene and one or more C.sub.3 to C.sub.28 alpha-olefins which have been solution-grafted in the presence of a free-radical initiator with an ethylenically-unsaturated carboxylic acid material at an elevated temperature, preferably in an inert atmosphere, and thereafter reacted with a polyfunctional material reactive with carboxy groups, such as (a) a polyamine, (b) a polyol or (c) a hydroxyamine or mixtures thereof, to form polymeric reaction products. The reaction products are described as sludge-dispersing additives for hydrocarbon fuels and lubricating oils.
U.S. Pat. No. 4,032,700 describes a process for preparing aminated polymers which includes halogenating a copolymer of ethylene, a C.sub.3 to C.sub.18 a straight or branched chain alpha-chain olefin and a C.sub.5 to C.sub.14 acyclic or alicyclic non-conjugated diolefin and thereafter reacting said copolymer with an amine. The additives so produced are described as dispersants for hydrocarbon fuels or lubricants and as multifunctional dispersant-viscosity index improvers for lubricants. There is no express or implied recognition of using the additives as antioxidants in diesel fuel formulations to improve the stability of same.
U.S. Pat. No. 4,919,684 describes a stable middle distillate fuel-oil composition which includes (a) a major portion of a middle distillate fuel oil and (b) a minor amount, as a storage stabilizing additive, of N-3-(3,5-di-t-butyl-5-hydroxybenzene) propyl succinimide of a copolymer and maleic anhydride graft.
U.S. Pat. No. 4,919,685 describes a stable middle distillate fuel-oil composition which includes (a) a major portion of a middle distillate fuel oil and (b) a minor amount, as a storage stabilizing additive, of an aliphatic N(N',N'-dimethylaminopropyl) succinimide of a copolymer and maleic anhydride graft.
It is, therefore, our understanding that a method for stabilizing diesel fuels by substantially eliminating oxidation and, particularly, high temperature oxidation of such fuels, in the manner described below has heretofore been unavailable.